Some ultra-high pressure wells that produce gas and liquid together employ an electric submersible pump (ESP) or artificial lift mechanism to bring the liquids to the surface. On occasion the ESP or artificial lift mechanism has to be removed for maintenance or replacement. Typically the ESP or artificial lift mechanism is located in the main bore that may or may not have multiple laterals. During normal operations, the produced liquids migrate into the artificial lift mechanism intake. Produced gas typically flows to surface, especially if under pressure. Known separation equipment separates the liquid and gas phases at the surface.
If the artificial lift mechanism needs to be pulled the gas production has to be curtailed as well control techniques for the well need to hold back the high formation pressures as the artificial lift mechanism is pulled out from the well in a safe manner with the formation pressures isolated. This can be accomplished by killing the well with heavy fluids or pulling the artificial lift mechanism through formation isolation valves and closing such valves as the artificial lift mechanism is pulled up past such valves. No matter which way the replacement of the artificial lift mechanism is accomplished, the gas production from the well is interrupted and liquids accumulate in the borehole. If this happens, it is sometimes difficult to regain the previous production rates.
It is known in the field of oil and gas production to use artificial lift techniques to increase the flow rate of wells having a reduced bottom hole pressure. One method of artificial lift is to incorporate an ESP in the production tubing to pump the fluids to the surface of the well. The ESP can either be directly in the production tubing or located in parallel with bypass tubing. In this second arrangement a Y-Block is located in the production tubing wherein the ESP is supported from a first limb and the bypass tubing is supported from the second limb. The parallel arrangement is used when equipment needs to be run to a location below the ESP in the well. One disadvantage of such systems is the space they take up making them impractical for many applications.
A known disadvantage of these systems even when they can be practically employed as space is not a concern, occurs when the ESP is switched off. On switching off the pump, the fluid column in the production tubing above ESP drains back through the pump, which can cause reverse rotation of the pump and sand can settle in the pump. As such, scale, wear and debris build up at the ESP causing damage and potential failure of the ESP. A further disadvantage of the parallel arrangement is that a blanking plug must be installed in the bypass tubing at the isolation packer for well control. When the ESP is in use to prevent produced fluids re-entering the well through the bypass tubing, an auto-check or flapper valve in the Y-Tool is used to control the flow. This is a costly exercise as a wireline or other string must be inserted through the production tubing to carry the plug to the isolation packer or device.
An automatic blanking completion tool has been proposed in GB 2 327 961 in the form of a modified Y-Block which automatically seals the ESP, when the ESP is switched off, and seals the bypass when the ESP is running. This tool operates on the differential pressure between the bypass tubing and the ESP. A hinged flapper or a rolling ball mechanism is mounted in the Y-Block at the point where the two limbs meet. The flapper or a rolling ball mechanism is biased towards an open position where it covers the access to the ESP. When the ESP is switched on, the increase in pressure, forces the flapper or a rolling ball mechanism over to cover the access to the bypass tubing. Additionally when the ESP is switched off, the bias will return the flapper or a rolling ball mechanism to cover the ESP. As fluid pressure operates the tool, no intervention is required and the tool is automatic.
While the automatic blanking tool advantageously prevents detritus entering the ESP when not in use detritus falling on the flapper or a rolling ball mechanism when in the closed position will automatically be ejected into the ESP when the ESP is switched off. This can damage the ESP as described above.
An improvement claiming to address such problems is discussed in WO/2007/026142A1. These systems are expensive, still have reliability issues and cannot fit it many applications without forcing the borehole to be significantly enlarged to accommodate the Y-Block.
The present invention seeks to provide a system where the gas production can continue when the ESP or artificial lift mechanism is removed. The ESP or artificial lift mechanism is disposed in a discrete bore from the main borehole sump but is in fluid communication with the sump or wellbore. The sump or wellbore can serve multiple wells that each may have multilaterals in such an orientation that permits the produced gas to move up to the surface as the liquids or condensate produced collects in the sump or wellbore. One or more boreholes can share a common sump or wellbore and each well need not necessarily have multiple laterals. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.